1. Field of the Invention
The present invention relates to a display device, and more particularly to a display device with an optical sensing frame wherein a waveguide unit having a double-layer structure including a light-receiving layer and a light-emitting layer is applied to realize structural simplification and increase an active area, and a method for detecting touch using the same.
2. Discussion of the Related Art
In general, a touch panel forms an interface between information and communication devices using a variety of displays and a user. The touch panel is an input device which interfaces with an apparatus by directly contacting a screen by hand or with a pen. A touch panel is an input apparatus which can be manipulated by contacting a button displayed on a display with a user's finger. Accordingly, a touch panel is easily utilized by users of all ages. Touch panels are utilized in a variety of applications including issuing machines in banks or government offices, various medical apparatuses, electronic tour guides, and electronic traffic guides.
Based on the manner in which touch is sensed, touch panels are divided into resistive touch panels, micro capacitive touch panels (glasses), ultrasonic touch panels (glasses), infrared touch panels, etc.
First, the resistive touch panel is composed of two conductive transparent layers, i.e., a lower layer made of a glass or plastic coated with a conductive material and an upper layer made of a film coated with a conductive material. The two layers are electrically isolated by a predetermined distance through a micro-printed spacer. In accordance with the resistive touch panel, when a predetermined voltage is applied to the two layers coated with a conductive material and an upper plate is touched by hand or with a pen, an upper plate (X axis) and a lower plate (Y axis) undergo variations in resistance depending on the position of touch, and a controller present therein calculates the positions of the upper plate (X axis) and lower plate (Y axis) that undergo resistance variation to display X and Y coordinates on a screen, and data may be inputted by the touch screen.
The micro capacitive touch panel includes a transparent glass sensor thinly coated with a conductive material. The conductive coating layer includes electrode patterns finely printed along an edge of the conductive coating layer. A protective coating film made of a transparent glass is also applied in close contact with an upper side of the conductive layer to protect and enclose the glass sensor. The micro capacitive touch panel operates such that a predetermined voltage is applied to a glass screen and the electrode patterns form a low voltage field on a surface of the touch sensor through the conductive layer. Therefore, when the user touches the screen with his or her finger, a micro-amperage current is generated at the touched portion. Further, a touch screen controller can determine the touched portion through proportional calculations using the amperage of the current because the current from each corner is proportional to a distance from the corner to the finger.
The ultrasonic wave touch panel is made entirely of glass. Therefore, as compared to other touch screens, in which the lifespan can be reduced via even minor scratches or abrasions on the surface, the ultrasonic wave touch panel is not influenced by surface damage or abrasion. Further, in the ultrasonic wave touch panel, a touch screen controller transmits 5 MHz electric signals to a transmitting transducer which generates ultrasonic waves. The generated ultrasonic waves are then passed through a panel surface by reflected lines. Therefore, when the user touches a surface of the touch screen, a part of the ultrasonic waves passing through the touched portion are absorbed by the user and loss of signals is transmitted to the controller through received signals and a digital map. Then, the controller calculates the coordinate values of the portions where the variation in the signals occurs. The above serial operations are performed with respect to the X-axis and the Y-axis, independently.
The infrared type touch panel uses the straightness effect of infrared rays, i.e., uses a principle in that infrared rays do not advance beyond an obstacle placed ahead of the rays. In more detail, infrared rays emitted in horizontal and vertical directions are obstructed at a portion touched by the user, and a controller determines the coordinate values of the X-axis and Y-axis of the infrared-obstruction. Thus, the infrared touch panel detects the touched portion through interruption of the infrared ray at a front side of the touch panel. Further, infrared rays are emitted from one side of the X-axis and the Y-axis and received at the other side of the X-axis and the Y-axis, thereby forming an invisible infrared matrix.
Although each type of panel has different advantages, mentioned above, infrared touch panels currently attract much attention because they require less pressure to be applied to the touch panels. Next, a related art infrared type touch panel will be described with reference to the annexed drawings.
FIG. 1 is a plan view illustrating an infrared touch panel according to the related art.
As shown in FIG. 1, the related art infrared touch panel, as mentioned above, forms an infrared ray (IR) matrix, a light-emitting portion 19 provided with a light-emitting waveguide 10 at two sides adjacent to a touch panel surface 14, and a light-receiving portion 20 provided with a light-receiving waveguide 16 at the other adjacent two sides.
The light-emitting portion 19 and the light-receiving portion 20 are provided with lenses 12 and 15 connected to the light-emitting and light-receiving waveguides 10 and 16, respectively, to straightly transfer light emitted and received through the respective waveguides to the matrix. The light-emitting waveguide 10 of the light-emitting portion 19 is provided at one side thereof with an LED light source 11 to transfer light thereto and a light splitter 18. The light-receiving portion 20 is provided at one side thereof with a photo sensor 17, connected to the light-receiving waveguide 16, to detect presence of touch. Here, the photo sensor 17 is provided with a photo sensor array to decide coordinates of a user's touch since photo sensor 17 is connected to the light-receiving waveguide 16 which is connected to both the X-axis and Y-axis.
In such a structure, the light-emitting portion 19 and the light-receiving portion 20 are provided at one side thereof with a light source 11 and a photo sensor 17, respectively. To connect the light source 11 and the photo sensor 17 to the waveguides 10 and 16 so as to transfer light in X-axis and Y-axis directions, line lengths of the waveguide far from the light source 11 and the photo sensor 17 as well as areas of the light-emitting portion 19 and the light-receiving portion 20 must inevitably be increased.
The aforementioned related art infrared touch panel has the several disadvantages. First, the light-emitting portion or light-receiving portion provided with the waveguide and lens should be arranged at four sides of the touch panel plane. For touch sensing, all configurations should be provided throughout all edges of the touch panel. Accordingly, location of elements is complicated and lengths of lines are increased. Due to these disadvantages, electric noise or EMI generated from display devices may affect touch systems. Second, the light-receiving portion and the light-emitting portion should be provided at two adjacent sides which complicates the structure and reduces an active area. Third, as the area of the touch panel increases, the number of pixels also increases, and more waveguides and lenses are required. An active area of the touch panel of a predetermined size is decreased. The touch panel at two respective sides thereof with the light-emitting portion and the light-receiving portion does not reflect active area efficiency of a display panel arranged in a lower region. As a result, the related art infrared touch panel is inapplicable to large-area display devices. In addition, the recent trend toward thin bezels inhibits realization of touch module-integrated displays due to the volume of the touch module.